Apparatus for heat treating sheet material



April 11, 1967 N, C, WYET'H 3,313,002

APPARATUS FOR HEAT TREATING SHEET MATERIAL Filed Aug. 4, 1965 UnitedStates Patent ilce ansatz 3,313,902 APPTUS FR HEAT TREATING SHEETMATERIAL Nathaniel Conyers Wyeth, Rosedale, Pa., assigner to E. l.

du Pont de Nemours and Company, Wilmington, Del.,

a corporation of Delaware Filed Aug. 4, 1965, Ser. No. 477,211 3 Claims.(Cl. l-lil) This invention relates to an apparatus for the uniformheat-treatment of porous sheet materials. In particular it concerns anapparatus for effecting such heat-treatment while maintaining arestraint on the surface of the sheet thereby preventing or minimizingany change in area dimensions.

The heat-treatment of porous sheet materials, such as non-woven fabricwebs or paper like sheet structures, is often required in order toactivate a binder material therein, to modify the surface for decorativeor smoothing effects, to cause spontaneous elongation of the constituent`fibers thereby developing liber crimp, or for other known purposes. Inmany instances the heattreatment requires the use of a closelycontrolled temperature and rapid attainment of that temperature in orderto prevent adverse effects upon resulting sheet material. An apparatusdesigned to achieve these objectives is that described in Huffman U.S.Patent No. 3,192,560. 'It is an object of the present invention toachieve these desirable objectives with a simpler piece of apparatus.

While non-woven fabrics can be bonded by any of the well known solvent,adhesive, or heat-bonding techniques, the latter in which the fibers areself-bonded at a multiplicity of fiber intersection points possessesdistinct advantages in terms of cost and the avoidance of the extrasteps which are otherwise needed to apply a binder material and remove avolatile carrier should one be used. Moreover, special effects can beoften achieved by self-bonding techniques which are not readilyattainable by other methods. A noticeable disadvantage of theselfsbonding techniques as heretofore practiced however, has been thelack of equipment which when employed in a continuous operation on acommercial scale will provide a high degree of precision required withrespect to temperature control. Thus, if the temperature is notconsistently maintained at a suliiciently high level, areas of thefabric may possess an inadequate number of satisfactorily strong bonds.Excessiveiy high temperatures, on the other hand, give rise tooverbonding even to the point where the liber structure collapses.Problems have also been experienced in preventing excessive fibershrinkage during bonding. Certain iibers have been observed to undergoexcessive shrinkage even when bonded under carefully controlledconditions. To obtain uniform products therefore, particular care mustbe exercised to ensure that the fibers in the sheet product are properlyrestrained during the heating operation.

It is accordingly an object of the invention to provide an apparatus forthe uniform heat-treatment of wide sheet materials under closelycontrolled temperature conditions. Another object of the invention is toprovide an apparatus for treating a continuous web of material which iscapable of supplying a large quantity of heat at a high rate within anarrow precisely controlled temperature range while the web is underrestraint to prevent shrinkage. A still further object of the inventionis to provide an apparatus for heat treating a continuous web ofmaterial by uniformly heating the web while maintaining restraint andrapidly cooling it after treatment.

The apparatus of this invention is best understood by reference to thefollowing figures in which:

FIGURE l shows a schematic representation of the apparatus in itssimplest form.

FGURES 2 and 3 show pneumatic roll embodiments composed of elongatedtubular elements arranged parallel to the roll axis and of a pluralityof closely spaced tires respectively.

ln FIGURE 1 the bonding apparatus comprises a compressible roll 2 havingan outer layer 49 of elastomeric material urged against a perforatedrotary drum 1 to provide an extended nip zone. The roll 2 containscoolant passageway ti for removing heat from the elastomeric material49. Drum 1 is a rigid relatively thick walled hollow cylinder made of asuitable corrosion resistant material such as a stainless steel alloy.At either end of cylindrical drum 1 and tlxedly attached thereto orintegral therewith are side members having flanges that may be rotatablyjournaled, for example, to the outer races of standard commercial typeantifriction bearings. Drum 1 may be rotatably driven through forceapplied to the side members or through other suitable means. A driveshaft connected to a side member and coupled by conventional couplingmeans to the output of a standard commercial variable speed electricmotor drive has been found satisfactory.

Hollow stationary beam 17 is located at the axis of drum l and extendsthrough the side members. Inlet means 7 comprising a pipe located withinbeam 17 is connected at one end with chamber 3, which is supported bybeam 17 and situated within the drum, and at the other with a heatedvapor source preferably high pressure steam. One end of the outlet means8, for the elimination of condensate, connects into the base of chamber3 and comprises a line carried within the interior of beam 17. The otherend of the line extends outside the machine to a suitable condensateremoval means. Beam 17 is further modified by opposed side openings 24into which one end of exhaust ducts 5 connect with beam 17 interior.Beam 17 thus serves as an exhaust conduit which accordingly is suitablyconnected at some remote point outside the machine to an exhaust blowerV(not shown). The upper ends of ducts 5 are narrow elongated openingswhich connect with drum apertures that are substantially entirely withinthe nip. The duct openings extend along the length of chamber 3 andadjacent the inside peripheral surface of drum 1.

Chamber 3 is a shallow rectangular box-like member that is stationaryand communicates with certain of the apertures in the drum Wall. Theupper face of chamber 3 is formed by a small section of the interior ofthe drum 1 surface while the perimeter of the upper face of chamber 3 isenclosed by a iloatable seal assembly 4 which frictionally abuts withthe internal surface of drum 1. Seal assembly 4 contines the effectivearea of treatment chamber 3 to a narrow rectangular band of the surfaceof drum 1 that will ordinarly extend substantially the entire length ofthe drum and is contained entirely within the nip. against the surfaceof drum 1 partly by a plurality of spaced compression springs 28 locatedat the bottom of the recess and by the pressure of the treatment fluidin chamber 3.

Seal assembly 4 is composed of a plurality of flat bars or elementsinterconnected to form a fluid tight barrier.

Patented Apr. ll, 196? Assembly 4 may be urged,

The elements may be made of a porous carbon composi-l tion impregnatedwith a fluorocarbon resinous material for low friction, long wear lifeand high thermal resistance. The elements are modied at their ends by atongue and groove configuration so thatrwhencoupled together there isample allowancefor relative movement and deection between individualelements without risk of creating a free path for steam leakage. Sealassembly 4 is retained within a matching recess in chamber 3 wall.

Shaft extensions of roll 2 are rotatably journaled in bearings (notshown). The shaft extensions of roll 2 may be the ends of a rigidtubular steel core 45 t-o which is welded a hollow cylindrical shell 46.Within the shell 46, another cylindrical baffle or wall 47 is affixedthat forms the coolant passageway 6 which communicates at one end withthe core 45 interior and at the opposite end with an inlet conduit 48.Hydraulic actuators (not shown) operating on the shaft of roll 2 causemovement relative to dmm 1.

Bonded to the external surface of shell 46 is a thick cover 49 ofelastomeric material. Any resilient material having high temperatureresistance and high fatigue life may be used. A synthetic hydrocarbonrubber manu factured by the Du Pont Company under the trade name Nordelis preferred because of its excellent resistance to wear and hightemperature steam. It is preferred for best results that cover 49 bemade relatively pliable, the softness ranging from between 45 to 65Shore A durometer.

The softness of cover 49 determines to a great extent the width of thenip formed between roll 2 and drum 1 and the magnitude of the forceurging the rolls together to form the nip. It will be recognized that acover 49 material excessively resilient will fail to conline the highpressure steam or other heat-treating fluid. Conversely a material toostiff requires tremendous nip pressures and will crush the fibrousproduct. As previously indicated, large amounts of internal frictionheat caused by high intensity flexing of the material rapidly degradesthe material. Most of these difficulties, however, may be over-come witha pneumatic roll structure where only a relatively thin membrane orsheath of elastomeric material is subjected to the distortion andflexing action. Moreover, stiffness characteristics of the roll areeasily adjusted by a simple regulation of the pneumatic pressure backingthe membrane.

FIGURE 2 illustrates an alternative pneumatic roll embodiment utilizinga support shell 50 and sheath 51 composition to enclose a plurality ofelongated tubular pneumatic elements S5. The elements are packed closelytogether parallel to the roll axis and when pressurized expandtightlyagainst each other to form a substantially uniform narrow -cellularpneumatic layer.

FIGURE 3 is a further embodiment of the pneumatic roll concept showingsupport shell 50 and reinforced sheath 51. The pneumatic portion iscomposed of a plurality toroidal elements 56 packed tightly side byside. The elements 56 are actually multi-ply auto tires without treadsbut containing inner tubes.

In operation, a foraminous belt 65 is trained around drum 1 from anupstream web formation area. Belt 65 greatly facilitates transfer of thefragilev sheet material which hereafter is described as web 64 in anessentially non-disturbed condition. Preparatory to actual treatment ofproduct, various adjustments `may be made to the machine to meet endproduct quality requirements.

At start up, an operator energizes the hydraulic actuators controllingmovement of the shaft and lowers the roll 2 closing the nip between therotary members sufficient to confine the steam to chamber 3. Coolantwater is introduced through inlet 48 into passageway 6 to control themaximum temperature of the cover 49 at the operating conditionsemployed. Drum 1 is driven at Ymachine components some moderate speed,as for example, about six yards per minute. A slightly subatmosphericcondition is established in the exhaust ducts 5 by an exhaust blower orsome other means. At this point, steam is introduced intotreatmentrcharnber 3 slowly so as to allow the cool to attain steamtemperatures. Steam pressure is increased at a rate which does notexceed a 46 C. difference in temperature between the steam and themachine parts. It is noted that during the build up of steam, the nippressure of roll Z is increased proportionately. After the desiredoperating pressure is attained, final adjustment of nip pressures anddrum l speed are made. f

In operation web 64 entering the nip is firmly restrained lneforecommunicating with the lsteam treatment zone. rl`he steep vsteampressure profile subjects the web 64 to rapid heating and cooling. Sincesignificant qualities of steam can be entrapped in the roll aperturesand web interstices, the suction of duct 5 on the downstream side ofchamber 3 draws off the vap-or and accelerates cooling before the web`64 restraint is released. After emerging from the ni the cooled web 64is separated from belt 65 under a slight tension and directed to eithera take up stand for winding into mill rolls or carried to otherdownstream processing. If desired, an upper screen belt, not shown,trained around roll 2 from an upstream web formation area andcooperating with belt 65 to sandwich the web while in the nip, may beemployed to modify the upper surface of the fibrous structure.

The bonding apparatus of the invention provides a relatively low cost,compact high productivity means for processing wide sheet material. Itis capable of handling and processing wide sheet material at high speedsunder precisely controlled conditions.

What is claimed is:

1. An apparatus for heat-treating a continuous length of sheet materialcomprising a compressible roll in rolling engagement with a hollow drumaround which is trained a foraminous belt over which a sheet advancesbetween the roll and drum, said drum having its circumferential surfaceinterrupted by perforations and said compressible roll being urgedagainst the drum and deformed thereby so as to form an extended nipzone, and residing within said drum a stationary fluid treatment chamberhaving an inlet for provision of hot treating fluid, the said chamberopening on the inner surface of the drum and communicating with drumperforations in the nip region to provide a heat-treatment area, sealsmounted on said chamber and operatively urged against theinner surfaceofthe drum so-that the heat-treatment uid in the chamber is confined tothe region of the nip, and exhaust means in the nip region adjacent theheat-treatment area for carrying away uid leakage past the seals andoutside of the heat-treatment area.

2. The apparatus of claim 1 wherein cooling means are provided for thecompressible roll for removal of internal heat generated in the roll bythe operation of said apparatus. n

3. Apparatus for heat-treating a continuous length of sheet materialcomprising a hollow drum having perforations in the circumferentialsurface thereof, a roll covered with a layer of resilient material, anda foraminous belt trained around the drum for supporting the sheetmaterial said roll being urged against the drum to provide a nip forreceiving and restraining the sheet material as it passes through, thenip being extended by deformation of the resilient outer layer of saidroll against the drum, the perforations of`the drum in the region of thenip communicating with a stationary fluid treatment chamber residingwithin said drum and having fluid inlet means, said chamber having sealsurged against the inside surface of the drum for confining theheat-treatment fluid to the nip region perforations of the drum andsuction means adjacent to the seals at the inner surface of said drumfor carryingl away uid leakage passed the 6 Seals and outside of theheat-treatment area whereby hot 2,952,033 9/ 1960 Goodwin 1S-1 fluidcontacts the sheet material substantially only while 3,230,287 1/1965Caron et al- 18-4 XR the sheet material is engaged by the nip. FOREIGNPATENTS References Cited by the Examiner 5 366920 3/1963 SwitzerlandUNITED STATES PATENTS References Cited by the Applicant 1,007,13710/1911 Palmer. UNITED STATES PATENTS 1,880,691 10/1932 Berry. 2,920,4061/1960 Vlgliarolo.

2,209,760 7/1940 Beffy- 10 WILLIAM J. STEPHENSON, Prima/y Examiner.

1. AN APPARATUS FOR HEAT-TREATING A CONTINUOUS LENGTH OF SHEET MATERIALCOMPRISING A COMPRESSIBLE ROLL IN ROLLING ENGAGEMENT WITH A HOLLOW DRUMAROUND WHICH IS TRAINED A FORAMINOUS BELT OVER WHICH A SHEET ADVANCEBETWEEN THE ROLL AND DRUM, SAID DRUM HAVING ITS CIRCUMFERENTIAL SURFACEINTERRUPTED BY PERFORATIONS AND SAID COMPRESSIBLE ROLL BEING URGEDAGAINT THE GRUM AND DEFORMED THEREBY SO AS TO FORM AN EXTENDED NIP ZONE,AND RESIDIDNG WITHIN SAID DRUM A STATIONARY FLUID TREATMENT CHAMBERHAVING AN INLET FOR PROVISION OF HOT TREATING FLUID, THE SAID CHAMBEROPENING ON THE INNER SURFACE OF THE DRUM AND COMMUNICATING WITH DRUMPERFORATIONS IN THE NIP REGION TO PROVIDE A HEAT-TREATMENT AREA, SEALSMOUNTED ON SAID CHAMBER AND OPERATIVELY URGED AGAINST THE INNER SURFACEOF THE DRUM SO THAT THE HEAT-TREATMENT FLUID IN THE CHAMBER IS CONFINEDTO THE REGION OF THE NIP, AND EXHAUST MEANS IN THE NIP REGION ADJACENTTHE HEAT-TREATMENT AREA FOR CARRYING AWAY FLUID LEADAGE PAST THE SEALSAND OUTSIDE OF THE HEAT-TREATMENT AREA.